In general, a typical screw press comprises a screw, also called an auger, rotating within a fixed cylindrical body comprising screen panels. A solid-liquid mixture to be treated is fed into an inlet end of the screw press. The auger conveys the mixture through the cylindrical body while pressing the mixture against the screens. Liquid and fine solids are collected from the outside of the screens. Retained solids and residual liquid are collected from an outlet end of the screw press. The cylindrical body is dismantled when the screens need to be cleaned.
In International Publication Number WO02/062564, a screw press is used to separate solids from sewage. A screw is driven by an electric motor. The direction of rotation of the screw is reversed periodically to clean the screw press.
In International Publication Number WO99/52704, a screw press has a cylindrical body made up of a stack of annular plates. Some of the plates are fixed and some of the plates are movable. An eccentric shaft passing through the stack of plates rotates when the auger rotates. The rotation of the eccentric shaft causes the movable plates to oscillate relative to the fixed plates.